System and method for sensorless control of electric machines using magnetic alignment signatures

Abstract

A system and method for position sensorless control of an AC electric machine is disclosed. A drive system for driving an AC electric machine provides a primary current excitation to drive the AC electric machine, the primary current excitation comprising a current vector having a magnitude and angle. The drive system injects a carrier signal to the AC electric machine that is superimposed onto the current vector, with the carrier signal being selected to generate a carrier response signal that has sensitivity to magnetic alignment information of the AC electric machine at its operating point. The drive system measures at least one magnetic alignment signature of the AC electric machine from the generated carrier response signal and controls an orientation of the current vector using the measured at least one magnetic alignment signature, so as to achieve a desired magnetic operation of the AC electric machine.

What is claimed is: 
     
       1. A drive system for driving an AC electric machine, the drive system comprising:
 an electric machine power converter configured to provide a primary current excitation to drive the AC electric machine, the primary current excitation comprising a current vector having a magnitude and angle; and 
 a control system separate from or incorporated into the electric machine power converter configured to:
 inject a carrier signal to the AC electric machine that is superimposed onto the current vector, with the carrier signal being selected to generate a carrier response signal that has sensitivity to magnetic alignment information of the AC electric machine at its operating point; 
 measure at least one magnetic alignment signature of the AC electric machine from the generated carrier response signal; and 
 control an orientation of the current vector using the measured at least one magnetic alignment signature, so as to achieve a desired magnetic operation of the AC electric machine. 
 
 
     
     
       2. The control system of  claim 1  wherein, in injecting the carrier signal, the control system is configured to perform a directional pulsating injection of the carrier signal on a current reference frame, the directional pulsating injection of the carrier signal comprising one of a pulsating current injection and a pulsating voltage injection. 
     
     
       3. The drive system of  claim 2  wherein, in injecting the carrier signal, the control system is configured to perform one or more of:
 a current frame d-axis injection where the carrier signal is aligned tangentially to the current vector; 
 a current frame q-axis injection where the carrier signal is aligned with the current vector; 
 a current frame injection with a variable injection angle; and 
 an alternating current frame d-axis and q-axis injection. 
 
     
     
       4. The drive system of  claim 3  wherein, for the directional pulsating injection, the at least one magnetic alignment signature comprises:
 at least one of a current frame d-axis inductance, a current frame cross inductance, and a composite of the current frame d-axis inductance and the current frame cross inductance, when the signal injector performs a current frame d-axis pulsating current injection; 
 at least one of a current frame q-axis inductance, a current frame cross inductance, and a composite of the current frame d-axis inductance and the current frame cross inductance when the signal injector performs a current frame q-axis pulsating current injection; 
 at least one of a pulsation axis inductance, a pulsation axis cross inductance, and a composite of the pulsation axis inductance and the pulsation axis cross inductance, when the signal injector performs a current frame current injection with a variable injection angle; and 
 at least one of a current frame cross inductance, a conditionally measured or blended measured current frame d-axis inductance and current frame q-axis inductance, and a composite of the current frame cross inductance and the conditionally measured or blended measured current frame d-axis inductance and current frame q-axis inductance, when the signal injector performs an alternating current frame d-axis and q-axis current injection. 
 
     
     
       5. The drive system of  claim 3  wherein, for the directional pulsating injection, the at least one magnetic alignment signature comprises:
 at least one of a current frame d-axis reluctance, a current frame cross reluctance, and a composite of the current frame d-axis reluctance and the current frame cross reluctance, when the signal injector performs a current frame d-axis pulsating voltage injection; 
 at least one of a current frame q-axis reluctance, a current frame cross reluctance, and a composite of the current frame q-axis reluctance and the current frame cross reluctance, when the signal injector performs a current frame q-axis pulsating voltage injection; and 
 at least one of a pulsation axis reluctance, a pulsation axis cross reluctance, and a composite of the pulsation axis reluctance and the pulsation axis cross reluctance, when the signal injector performs a current frame voltage injection with a variable injection angle; 
 at least one of a current frame cross reluctance, a conditionally measured or blended current frame d-axis reluctance and current frame q-axis reluctance, and a composite of the current frame cross reluctance and the conditionally measured or blended current frame d-axis reluctance and current frame q-axis reluctance, when the signal injector performs an alternating current frame d-axis and q-axis voltage injection. 
 
     
     
       6. The drive system of  claim 2  wherein, in injecting the carrier signal, the control system is configured to inject a pulsating high frequency voltage signal or current signal with angle compensation that reduces torque ripple in the AC electric machine; and
 wherein, for the injection of the pulsating high frequency voltage signal with angle compensation, the at least one magnetic alignment signature comprises at least one of a pulsation axis reluctance, a pulsation axis cross reluctance, and a composite of the pulsation axis reluctance and the pulsation axis cross reluctance; and 
 wherein, for the injection of the pulsating high frequency current signal with angle compensation, the at least one magnetic alignment signature comprises at least of a pulsation axis inductance, a pulsation axis cross inductance, and a composite of the pulsation axis inductance and the pulsation axis cross inductance. 
 
     
     
       7. The drive system of  claim 2  wherein, in injecting the carrier signal, the control system is configured to perform at least one of a profiled current frame current injection and a profiled current frame voltage injection, so as to customize a sensitivity of the magnetic alignment signature;
 wherein, for the profiled current frame current injection, the at least one magnetic alignment signature comprises at least of a pulsation axis inductance, a pulsation axis cross inductance, and a composite of the pulsation axis inductance and the pulsation axis cross inductance; and 
 wherein, for the profiled current frame voltage injection, the at least one magnetic alignment signature comprises at least one of a pulsation axis reluctance, a pulsation axis cross reluctance, and a composite of the pulsation axis reluctance and the pulsation axis cross reluctance. 
 
     
     
       8. The drive system of  claim 1  wherein, the control system is configured to perform a saliency tracking injection comprising at least one of a minimum inductance axis tracking injection and a maximum inductance axis tracking injection, the minimum inductance axis tracking injection being a saliency frame d-axis tracking injection and the maximum inductance axis tracking injection being a saliency frame q-axis tracking injection; and
 wherein, for the saliency tracking injection, the at least one magnetic alignment signature comprises one or more of a maximum inductance L max  and a minimum inductance L min . 
 
     
     
       9. The drive system of  claim 1  wherein, in injecting the carrier signal, the control system is configured to perform a rotating vector injection comprising at least one of a rotating vector current injection, a rotating vector voltage injection, and a, elliptical excitation in a current reference frame, the elliptical excitation being one of an elliptical injection with a fixed orientation or an elliptical injection with a rotating orientation that is varied based on the operating point of the AC electric machine and a desired sensitivity and torque ripple trade-off. 
     
     
       10. The drive system of  claim 9  wherein, for the rotating vector injection, the at least one magnetic alignment signature comprises at least one of, or a composite of, a maximum inductance L max , a minimum inductance L min , a composite signature comprising an average inductance L Σ  or average reluctance R Σ , a current frame d-axis inductance, a current frame q-axis inductance, a current frame cross inductance, a current frame d-axis reluctance, a current frame q-axis reluctance, and a current frame cross reluctance; and
 wherein measuring of the maximum inductance L max  and the minimum inductance L min , along with extraction of a saliency angle from the rotating vector injection, provides for conversion of the d-axis inductance and reluctance, q-axis inductance and reluctance, and cross inductance and reluctance to a desired reference frame of the AC electric machine. 
 
     
     
       11. The drive system of  claim 1  wherein, in injecting the carrier signal, the control system is configured to perform a blended injection comprising both a directional pulsating injection of the carrier signal on a current reference frame and a rotating vector injection. 
     
     
       12. The drive system of  claim 11  wherein, for the blended injection, the at least one magnetic alignment signature comprises at least one of, or a composite of, a current frame d-axis inductance, a current frame cross inductance, a current frame d-axis reluctance, a current frame d-axis reluctance, a current frame cross reluctance, and one or more of a conditionally measured or blended current frame q-axis inductance, current frame q-axis reluctance, maximum inductance L max  minimum inductance L min , and average inductance L Σ . 
     
     
       13. The drive system of  claim 1  wherein the control system is configured to:
 convert the carrier response signal to lower frequency signal than the carrier signal, so as to eliminate a carrier modulation frequency; 
 low pass filter the converted carrier response signal to determine vector components of the carrier response signal; and 
 extract the at least one magnetic alignment signature from the vector components of the carrier response signal. 
 
     
     
       14. The drive system of  claim 1  wherein, for each respective magnetic alignment signature of the at least one magnetic alignment signature, the control system is configured to:
 perform a forward mapping operation for a plurality of desired operating points for the AC electric machine to determine a desired magnetic alignment signature value and desired signature error gain for the magnetic alignment signature; and 
 estimate a magnetic alignment error based on the magnetic alignment signature, the desired magnetic alignment signature value, and the desired signature error gain. 
 
     
     
       15. The drive system of  claim 1  wherein, for each respective magnetic alignment signature of the at least one magnetic alignment signature, the control system is configured to:
 perform a reverse mapping operation for the magnetic alignment signature, at a desired operating point for the AC electric machine, to generate an estimated magnetic alignment signal; and 
 estimate a magnetic alignment error based on the estimated magnetic alignment signal and based on a current angle of the desired operating point for the AC electric machine. 
 
     
     
       16. The drive system of  claim 1  wherein, when the at least one magnetic alignment signature comprises multiple magnetic alignment signatures, the drive system is configured to:
 estimate a magnetic alignment error for each of the multiple magnetic alignment signatures; and 
 perform a soft blending operation when switching from use of a first magnetic alignment signature for controlling the orientation of the current vector to use of a second magnetic alignment signature for controlling the orientation of the current vector the soft blending operation reducing a transient response during switching of magnetic alignment signatures. 
 
     
     
       17. The drive system of  claim 1  wherein the control system is configured to determine a preferred injection method for injecting the carrier signal and select one or more specific magnetic alignment signatures of the at least one magnetic signature to control the orientation of the current based on one or more of the operating point of the AC electric machine and a dynamic state of the AC electric machine. 
     
     
       18. The drive system of  claim 1  wherein the magnetic alignment information includes at least one of a torque of the AC electric machine, the angle of the current vector in reference to a stator flux, the angle of the current vector in reference to a rotor flux, and the angle of the current vector in reference to a rotor pole axis. 
     
     
       19. The drive system of  claim 1  wherein the AC electric machine comprises one of an interior permanent magnet (IPM) machine, a permanent magnet (PM) assisted synchronous reluctance machine, a synchronous reluctance machine, and an inductance machine. 
     
     
       20. A vehicle comprising the drive system of  claim 1  therein, and wherein the AC electric machine comprises a traction motor driven by the drive system. 
     
     
       21. A method for position sensorless control of an AC electric machine, the method comprising:
 causing a drive system to generate a primary current excitation to drive the AC electric machine, the primary current excitation comprising a current vector having a current magnitude and current angle; 
 causing the drive system to superimpose high-frequency carrier voltage or current onto the current vector to generate a selected carrier response current or voltage, respectively, that has sensitivity to magnetic alignment information of the AC electric machine; 
 causing the drive system to determine one or more magnetic alignment signatures of the AC electric machine from the carrier response current or voltage; and 
 causing the drive system to control the current angle of the current vector driving the AC electric machine based on the one or more magnetic alignment signatures, in order to achieve a desired magnetic operation of the AC electric machine. 
 
     
     
       22. The method of  claim 21  wherein superimposing the high-frequency carrier voltage or current comprises injecting the high-frequency carrier voltage or current on a current reference frame of the AC electric machine, according to one or more of a d-axis injection, a q-axis injection, a variable injection angle, a profiled angle injection, and an alternating d-axis and q-axis injection. 
     
     
       23. The method of  claim 21  wherein superimposing the high-frequency carrier voltage or current comprises performing a rotating vector injection, the rotating vector injection comprising injecting one or more of a rotating voltage vector, a rotating current vector, and an elliptical injection in a current reference frame, the elliptical injection comprising one of an elliptical injection with a fixed orientation and an elliptical injection with a rotating orientation. 
     
     
       24. The method of  claim 21  wherein superimposing the high-frequency carrier voltage or current comprises performing a saliency tracking injection according to one of a minimum inductance axis tracking injection and a maximum inductance axis tracking injection, the minimum inductance axis tracking injection being a saliency frame d-axis tracking injection and the maximum inductance axis tracking injection being a saliency frame q-axis tracking injection. 
     
     
       25. The method of  claim 21  wherein superimposing the high-frequency carrier voltage or current comprises performing a blended injection that includes both a pulsating injection of the high-frequency carrier voltage or current on a current reference frame and a rotating vector injection of the high-frequency carrier voltage or current. 
     
     
       26. The method of  claim 21  wherein the one or more magnetic alignment signatures comprises a signature or signatures other than a saliency angle, with the one or more magnetic alignment signatures comprising at least one of a current frame d-axis inductance, a current frame q-axis inductance, a current frame cross inductance, a current frame d-axis reluctance, a current frame q-axis reluctance, a current frame cross reluctance, a maximum inductance L max , a minimum inductance L min , an average inductance L Σ , and a composite of two d-axis, q-axis, or cross-inductances or reluctances. 
     
     
       27. A drive system for use with an AC electric machine not having suitable sensitivity for saliency tracking sensorless control, the drive system comprising:
 an electric machine power converter configured to generate a primary excitation current vector to drive the AC electric machine, the primary excitation current vector having a current magnitude and current angle; and 
 a control system configured to:
 inject a carrier signal onto the primary excitation current vector, the carrier signal comprising one of a carrier voltage and a carrier current that is superimposed on the primary excitation current vector; 
 measure at least one magnetic alignment signature of the AC electric machine that is derived from a carrier response signal generated from the injected carrier signal; and 
 control an orientation of the primary excitation current vector using the measured at least one magnetic alignment signature, so as to achieve a desired magnetic operation of the AC electric machine. 
 
 
     
     
       28. The drive system of  claim 27  wherein the carrier response signal has sensitivity to magnetic alignment information of the AC electric machine, the magnetic alignment information including at least one of a current angle of the primary excitation current vector, an angle between the primary excitation current vector and a rotor angle of the AC electric machine, and a torque of the AC electric machine. 
     
     
       29. The drive system of  claim 27  wherein the injected carrier signal comprises a pulsating voltage vector or pulsating current vector, with the pulsating voltage vector or pulsating current vector being injected onto one or more of:
 a current frame d-axis, a current frame q-axis, a variable angle on the current frame, a profiled angle on the current frame, and/or the current frame d-axis and q-axis in an alternating fashion; and/or 
 a saliency frame minimum inductance axis and/or a saliency frame maximum inductance axis, with the pulsating voltage vector or pulsating current vector tracking the minimum inductance axis and/or a saliency frame maximum inductance axis. 
 
     
     
       30. The drive system of  claim 27  wherein the injected carrier signal comprises a rotating voltage vector, a rotating current vector, and/or an elliptical excitation, the elliptical excitation being an elliptical excitation with a fixed orientation and/or an elliptical excitation with a rotating orientation.